Solar collector apparatus may be broadly classified into two different types, the first of which is the continuously movable type which is designed to continuously track the movement of the sun throughout the solar day, and the second of which is the stationary type which is fixedly adjusted with respect to the sun's trajectory for a particular solar season of the year. In both cases, the particular latitude of the terrestial location at which the collector is disposed is also taken into account.
In connection with the first type of collector, the efficiency of such collectors is, as may be expected, quite high due to the fact that the collector, being continuously movable along an arc corresponding to the sun's trajectory, is always disposed at an optimum position relative to the sun whereby the maximum solar energy may be collected. Such collector systems, however, employ altazimuth motor-driven tracking devices which are quite expensive and therefore involve considerable initial construction and erection expenditures. Consequently, such devices are only normally employed within sophisticated industrial or commercial systems.
In connection with the second type of collector, while the cost of the systems employing such collectors is substantially less than those systems employing solar tracking collectors, the efficiency of these fixed collectors is quite low. The reason for this may best be appreciated from FIG. 1 of the drawings. As shown in the figure, a conventional solar collector of the stationary type is shown as comprising a flat plate type collector. An operational characteristic of such conventional collectors is that during the early morning and evening hours, such as, for example, at 8:00 A.M. or 6:00 P.M., the solar rays strike the collector plate, generally indicated by the reference character 10, at an angle of incidence approximating 10.degree., as shown, for example, by solar ray 12. The ray is deflected by the flat plate collector, and consequently, solar energy is not transmitted to the absorber structure of the collector apparatus. It has been determined, in fact, that such flat plate collectors will not normally begin to actually collect a substantial amount of solar energy until the angle of incidence of the solar rays approximates 40.degree. as shown for example by solar ray 14. Under such circumstances, approximately 40% of the solar energy is reflected while 60% of the energy is absorbed. The absorption percentage of course increases as the angle of incidence approaches 90.degree..
The important consideration to be appreciated by the foregoing is that during early morning and evening hours, virtually no solar energy is able to be absorbed by conventional flat plate, stationary collectors. Similar results will likewise prevail during the winter solar season, as experienced in the Northern Hemisphere, due to the fact that the incidence of the solar energy is acute in a manner similar to early morning and evening hours. As a result of these circumstances, the efficiency of such flat plate, stationary collectors is unacceptably low whereby the commercial acceptance of such collectors is correspondingly low.